This invention relates to a storage system having a disk drive and a disk controller, and more particularly, to a technique of managing differential snapshots.
In recent years, storage systems have a snapshot function in order to protect data preserved in an operational volume. The snapshot function creates a snapshot of an operational volume at a specific point in time. Well-known snapshot functions are the full-copy snapshot function and the differential snapshot function.
The differential snapshot function is disclosed in JP 2004-342050 A according to which a storage system stores, in a differential volume, differential data between data in an operational volume and a differential snapshot. The storage system combines differential data preserved in the differential volume with data in the operational volume to provide a differential snapshot.